[tip:efi/core] arm64/efi: Ignore EFI_MEMORY_XP attribute if RP and/or WP are set

[tip-bot for Ard Biesheuvel <tipbot@zytor.com>]

Commit-ID:  1e9de1d2207d67b97bb0b62e38454b663d6542fa
Gitweb:     https://git.kernel.org/tip/1e9de1d2207d67b97bb0b62e38454b663d6542fa
Author:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
AuthorDate: Tue, 2 Jan 2018 18:10:39 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Jan 2018 14:03:48 +0100

arm64/efi: Ignore EFI_MEMORY_XP attribute if RP and/or WP are set

The UEFI memory map is a bit vague about how to interpret the
EFI_MEMORY_XP attribute when it is combined with EFI_MEMORY_RP and/or
EFI_MEMORY_WP, which have retroactively been redefined as cacheability
attributes rather than permission attributes.

So let's ignore EFI_MEMORY_XP if _RP and/or _WP are also set. In this
case, it is likely that they are being used to describe the capability
of the region (i.e., whether it has the controls to reconfigure it as
non-executable) rather than the nature of the contents of the region
(i.e., whether it contains data that we will never attempt to execute)

Reported-by: Stephen Boyd <sboyd@codeaurora.org>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tyler Baicar <tbaicar@codeaurora.org>
Cc: Vasyl Gomonovych <gomonovych@gmail.com>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180102181042.19074-3-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/arm64/kernel/efi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 82cd075..f85ac58 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -48,7 +48,9 @@ static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
 		return pgprot_val(PAGE_KERNEL_ROX);
 
 	/* RW- */
-	if (attr & EFI_MEMORY_XP || type != EFI_RUNTIME_SERVICES_CODE)
+	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
+	     EFI_MEMORY_XP) ||
+	    type != EFI_RUNTIME_SERVICES_CODE)
 		return pgprot_val(PAGE_KERNEL);
 
 	/* RWX */